Bertrand served as president of the Massachusetts Audubon Society. During his tenure, the organization almost tripled its membership to 64,000 households and added 20,000 acres of protected land to its holdings. He also initiated and founded the Programme For Belize, a non-profit that protects a quarter-million acres of tropical wildlife habitat.

From 1986 to 1994, Bertrand served on the Board of Directors of the International Council on Bird Preservation. When ICBP became BirdLife International, Bertrand was its first chairman. He has served on the National Audubon Society Board of Directors and was one of the original founders of the American Bird Conservancy.